This invention relates generally to the production of positron sources, and more particularly, to a method and apparatus for separating radioactive Na from Al and collecting the Na, particularly for use in intense slow positron beams.
The study of positrons and their interaction with matter has yielded several actual and potential applications for slow positron beams. However, some of the applications currently under consideration require intense positron beams for their success. The production and study of anti-hydrogen, positron synchrotron light sources, and positron microscopy are a few examples of such fields of study where intense slow positron beams would be quite useful.
The radioactive isotope .sup.22 Na is an important source of positrons. The current methods for isolating this material involve adding rather large amounts of reagents to target material in order to bring target, product, and impurities into solution. Then the solution is treated to obtain the product, which is often contaminated by sodium from the reagents. Relatively large volumes of waste are produced. Some of the reagents are sensitive to decomposition under intense radiation.
As indicated, one of the most attractive sources for laboratory use is .sup.22 Na, which combines a relatively long (2.6 yr.) half-life with high (90%) positron emittance. Currently, the primary technique for producing large amounts of .sup.22 Na involves bombarding pure Al with high energy (800 MeV) protons. There is a need for a process or system by which .sup.22 Na can be simply and inexpensively separated from Al.
The production of a Na source involves a four step process: (1) separation of Na from Al; (2) collection of the separated Na; (3) purification of the collected Na; (4) deposition and sealing of the source. The purification step (step 3) involves a well known technology--ion exchange chromatography--and therefore does not present any significant problems in the overall process. In addition, a process for accomplishing the deposition and sealing of the source (step 4) is readily available. There is a need, however, for a process which accomplishes the step of collecting the Na (step 2).
It is, therefore, an object of this invention to provide a radioactive system useful for producing a .sup.22 Na source.
It is another object of this invention to provide an improved source of positrons.
It is also an object of this invention to provide a system for producing a component of a system which can be applied to the production of an intense beam of slow positrons.
It is additionally an object of this invention to provide a system for separating Na from Al where high levels of radiation are involved.
It is yet a further object of this invention to provide a system for separating radioactive Na from Al without introducing significant amounts of inactive Na.
It is also another object of this invention to provide a system for separating radioactive Na from Al which does not require the use of additional reagents.
It is yet an additional object of this invention to provide a system for separating radioactive Na from A1 which does not result in significant waste.
It is still another object of this invention to provide a system for separating radioactive Na from Al which is relatively insensitive to radiation.